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Re: st: Not sure how to interpret -somersd- results


From   "Jain, Monica (HarvestPlus)" <M.Jain@cgiar.org>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Not sure how to interpret -somersd- results
Date   Thu, 3 Oct 2013 15:39:06 +0000

Thanks so much Roger for the clarification on interpretation and also for the suggestion on using asymmetric confidence intervals. I am also looking at the distribution of calories from non-staples  (calnstp) for children 6-23 months and 3-5 years separately,. I run the following command for height z-scores and calories from non-staple for 3-5 years children. For calories from non-staples for 6-23 months, I also run a similar command, which is not shown for brevity sake. 

       somersd year haz calnstp , cluster(district) transf(z) tdist

and I get the following results

Somers' D with variable: year
Transformation: Fisher's z
Valid observations: 627
Number of clusters: 4
Degrees of freedom: 3

Symmetric 95% CI for transformed Somers' D
                                   (Std. Err. adjusted for 4 clusters in dist)
------------------------------------------------------------------------------
                                            |              Jackknife
        year                            |      Coef.       Std. Err.            t       P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       Haz (3-5 years)        |   .3743973   .049804         7.52      0.005     .2158966     .532898
calnstp	(3-5 years)        |   .3376242  .0966604	3.49      0.040     .0300076    .6452408  
calnstp (6-23 months)  |   .2093922    .095348        2.20      0.116    -.0940477     .512832
-------------+----------------------------------------------------------------

Asymmetric 95% CI for untransformed Somers' D
                                                Somers_D           Minimum        Maximum 
       Haz (3-5 years)            .35783201          .21260359        .48759325
calnstp	(3-5 years)	.32535471	.02999857	.56845738
calnstp (6-23 months)  	.20638464	-.09377136	.47214883

Since the asymmetric confidence interval for height z-score does not contain zero, as you mentioned I can say that 2006 child height z-scores stochastically dominate 1996 child height z-scores at 5% level of significance.  For 3-5 years children, the 2006 calories from non-staples stochastically dominants 1996 calories from non-staples at 5% level of significance. However, for 6-23 months children this is not true as the confidence interval contains zero. Am I right in my interpretation of the above results?

Can I say anything about statewise dominance from the above results?

Monica Jain
Postdoctoral Fellow
HarvestPlus, IFPRI
2033 K Street, NW
Washington, DC 20006 (USA)
+1 (202) 862-4690 

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